JP2840314B2 - Projection exposure equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus, and more particularly, to an IC, L
The present invention relates to a projection exposure apparatus that projects a circuit pattern image of a reticle onto a wafer and is used when manufacturing a semiconductor device such as an SI.

(Prior art)

In a projection exposure apparatus for manufacturing semiconductor devices such as IS and LSI, it is important to improve the overlay accuracy of a pattern formed on a wafer in a previous process and a pattern image projected on the wafer by a projection optical system. It is an issue. As a factor influencing the overlay accuracy, the present applicant has disclosed in Japanese Patent Laid-Open No.
As shown in Japanese Patent No. 620, there is a projection magnification error and a distortion error of a pattern image. However, conventionally, there is no projection exposure apparatus capable of favorably correcting both the projection magnification error and the symmetric distortion.

[Summary of the Invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a projection exposure apparatus capable of favorably correcting both a projection magnification error and a distortion error of a pattern image.

The projection exposure apparatus of the present invention is a projection exposure apparatus that projects a pattern of a first object onto a second object by a projection optical system in which both the object side and the image side are telecentric. The symmetrical distortion and the projection magnification are changed by moving a close lens in the direction of the optical axis of the projection optical system, and the projection magnification is not changed by moving the first object in the direction of the optical axis of the projection optical system. And adjusting means for adjusting the symmetric distortion and the projection magnification by changing the symmetric distortion.

As is apparent from the configuration of the projection exposure apparatus, in the present invention, symmetric distortion is reduced in a projection exposure apparatus that projects a pattern of a first object onto a second object by a projection optical system in which both the object side and the image side are telecentric. As a new technique for adjusting, there is provided means for changing the symmetric distortion without changing the projection magnification by moving the first object in the optical axis direction of the projection optical system.

Some features and specific configurations of the projection exposure apparatus are described in detail in the following embodiments.

〔Example〕

FIG. 1 is a schematic view showing an embodiment of the projection exposure apparatus of the present invention.

In FIG. 1, 1 is a reticle on which a circuit pattern is drawn, 2 is a reticle chuck that sucks and holds the reticle 1,
3 is a reticle driving device attached to the reticle chuck 2,
4 is a reticle stage that supports the reticle driving device 4;
Reference numeral 5 denotes a reduction projection lens system in which both the object side and the image side are telecentric, 6 denotes a lens of the projection lens system 5 which is disposed close to the reticle 1 (hereinafter, referred to as a "field lens 6"), and 7 denotes a projection lens system. 5 is a lens system composed of several other lenses, 8 is a field lens
A lens driving device for moving in the direction of the optical axis AX, a wafer 9 coated with a photosensitive material such as a resist, a wafer chuck 10 for sucking and holding the wafer 9, a wafer driving device 11 mounted on the wafer chuck 9, and a wafer driving device 12 A wafer stage which indicates the apparatus 11 and is movable in a plane orthogonal to the optical axis AX of the projection lens system 5 is shown.

The reticle driving device 3 and the wafer driving device 11 each include a piezoelectric element or the like, and the reticle driving device 3 displaces the reticle chuck 2 in the optical axis AX direction of the projection lens system 5 to move the reticle 1 in the optical axis AX direction. The wafer chuck 10 is displaced in the optical axis AX direction of the projection lens system 5 by the driving device 11 to move the wafer 9 in the optical axis AX direction. On the other hand, the lens driving device 8 moves the field lens 6 in the optical axis AX direction of the projection lens system 5 using air pressure. Since the specific structure of the lens driving device 8 is disclosed in Japanese Patent Application Laid-Open No. 62-32613 by the present applicant,
Here, the description is omitted.

The driving of the reticle chuck 2 by the reticle driving device 3 is performed based on a signal from the reticle driving control system 13, and at this time, the position of the reticle 1 in the optical axis AX direction is detected by the reticle position detector 15. Similarly, the driving of the field lens 8 by the lens driving device 8 is performed based on a signal from the lens drive control system 16, and at this time, the position of the field lens 8 in the optical axis AX direction is determined by the lens position detector 17. Is detected. The reticle position detector 15 and the lens position detector 17 can be constituted by various position detectors such as an optical encoder. The wafer chuck 10 is driven by the wafer driving device 11 based on a signal from the wafer drive control system 14. At this time, the optical axis AX of (the surface of) the wafer 9
The position in the direction is detected by the focus detector 18. The focus detector 18 is composed of an air sensor or an optical sensor conventionally used in this type of projection exposure apparatus. Reticle position detector 15, lens position detector
The signals from the focus detector 17 and the focus detector 18 are input to the microprocessor 23. On the other hand, a pressure sensor 19, a temperature sensor 20, and a humidity sensor 21 are provided to detect changes in the atmospheric pressure, temperature, and humidity around the projection lens system 5,
A lens temperature sensor 22 is provided to detect a temperature change due to light absorption of the projection lens system 5, and signals from these various sensors 19, 20, 21, and 22 are also input to the microprocessor 23. Further, the reticle drive control system 13, the lens drive control system 16, and the wafer drive control system 14 are controlled by the microprocessor 23.

Reference numeral 24 denotes an illumination system for illuminating the circuit pattern of the reticle 1 with uniform illuminance. The illumination system 24 includes a KvF excimer laser that emits a laser beam having a wavelength λ = 248.4 nm as a light source for exposure. The laser light from the illumination system 24 is directed onto the wafer 9 via the reticle 1 and the projection lens system 5, and the circuit pattern image of the reticle 1 is projected on the wafer 9. In the present embodiment, in order to perform projection exposure with laser light having a wavelength in the far ultraviolet region, each lens constituting the projection lens system 5 is synthesized with a high transmittance for light having a wavelength λ = 248.4 nm. Manufactured from quartz (SiO ₂ ).

FIG. 2 shows a specific configuration of the projection lens system 5. Figure 2 is a sectional view of the projection lens system 5, between the reticle 1 and the wafer 9, reference numeral G ₁ ~G 12 lens optical axis A represented by ₁₂
The projection lens system 5 is arranged along X. Lens shown by reference numeral G ₁ is that the field lens 6 of FIG. 1 is constituted by a single lens in FIG. 2. The lens group represented by the symbol G ₂ ~G ₁₂ corresponds to the lens system 7 of Figure 1.

Table 1 shows lens data of the projection lens system shown in FIG. In Table 1, Ri (i = 1 to 24) indicates the curvature (mm) of the i-th surface counted in order from the reticle 1 side, and Di indicates the i-th and i + 1-th counted in order from the reticle 1 side. axial thickness or axial distance between the surfaces a (mm), Ni (i = 1~12) is the refractive index of the lens G _{i (i} = 1~12). S ₁ is the axial air gap between the circuit pattern surface of the reticle 1 and the surface of the lens G _{1 on} the reticle 1 side, and S ₂ is the axial air space between the surface of the lens G _{12 on} the wafer 9 side and the wafer 9 surface. Indicates the interval.

Table 2, the lens G _i in the projection lens system shown in Table 1, the adjacent reticle 1 and the axial air space S ₂ between the lens G _1, the lens G ₁₂ and axial air distance between the wafer 9 S ₂ and to each other When
On-axis air gap D _2i between G _{i + 1} (i = 1 to 11) (i = 1 to 1)
The shift amount ΔSD of the image point at the image height of 10 mm on the image plane of the projection lens system due to the change of the symmetrical distortion when 1) is individually changed by 1 mm. ΔS
D ”. ) And the shift amount Δβ accompanying a change in the projection magnification
(Hereinafter referred to as “projection magnification change amount Δβ”) and the ratio | ΔSD / Δβ | of both. Note that the image point shifted in a direction away from the optical axis of the projection lens system is positive, and the image point shifted in a direction approaching the optical axis of the projection lens system is denoted by a negative sign.

In this example, we decided to aberration variation other than symmetric distortion aberration by adjusting both the small spacing S ₁ and distance D ₂ for adjusting the projection magnification symmetrical distortion based on Table 2.

Now, assuming that the amount of change in the interval S ₁ is ΔS ₁ and the amount of change in the interval D ₂ is ΔD ₂ , from Table 2, the amount of change in the symmetric distortion and the projection magnification ΔS
D and Δβ can be represented by the following equations.

Therefore, ΔD ₂ and ΔS ₁ are given by the following equations.

The change in the aberration of the projection lens system 5 due to the change in the interval S ₁ , that is, the change in the distance between the projection lens system 5 and the reticle 1 is smaller than the change in the paraxial amount such as the projection magnification and the focus position. The ratio of the variation of the paraxial amount, that is, Is small. This is because the inclination of the light ray in the projection lens system 5 is larger than the inclination of the light ray between the object plane and the projection lens system,
This is because when the air gap between the lenses changes, the difference in the incident height of the light beam on the refracting surface of the lens increases, so that the aberration change increases. Therefore, in this embodiment, the adjustment of the projection magnification is performed by moving the lens G ₁ (field lens 6).
The adjustment of the distances S ₁ and D ₂ is mainly performed, and the adjustment of the distortion is performed mainly by the distance S ₁ by moving the reticle 1, whereby the projection magnification error and the symmetric distortion error in the projection exposure apparatus are reduced. Correct both.

Returning to FIG. 1, a method of correcting a projection magnification error and a symmetric distortion error of a pattern image in the projection exposure apparatus will be described in detail.

The microprocessor 23 is programmed in its memory with formulas for calculating the projection magnification change amount Δβ and the distortion change amount ΔSD of the projection lens system 5, and the respective calculation formulas are atmospheric pressure, temperature, humidity, The variation of the temperature of the projection lens system 5 from a predetermined reference value is a variable. The above formula (2) is also programmed in this memory, and the amount of movement of the field lens 6 and the amount of movement of the reticle 1 are obtained by substituting the values of β and ΔSD into the formula (2). . The equations for calculating the values of Δβ and ΔSD based on the atmospheric pressure, the temperature, the humidity, and the temperature change of the projection lens system 5 can be derived by experiments. On the other hand, the focus position of the pattern image by the projection lens system 5 depends on the atmospheric pressure, the temperature, the humidity around the projection lens system 5 and the projection lens system 5.
, And also changes depending on the positions of the reticle 1 and the field lens 6. Accordingly, in the present embodiment, a calculation formula for calculating the focus position fluctuation amount of the projection lens system 5 based on these fluctuation factors is programmed in the memory of the microprocessor 23, and the focus is calculated based on the calculation formula. I try to grasp the position accurately.

The microprocessor 23 receives the signals corresponding to the atmospheric pressure, the temperature, the humidity, and the lens temperature from the barometric pressure sensor 19, the temperature sensor 20, the humidity sensor 21, and the lens temperature sensor 22, and Based on this, the amount of movement of the reticle 1 and the amount of movement of the field lens 6 are determined. on the other hand,
From the reticle position detector 15 and the lens position detector 17,
A signal corresponding to the position of the reticle 1 and the field lens 6 (with respect to the optical axis AX direction) is transmitted to the microprocessor 23
Is input to Microprocessor 23 is reticle 1
Is input to the reticle drive control system 13, and the position signal of the field lens 6 and the signal corresponding to the amount of movement of the field lens 6 are input to the lens drive control system 16. Then, the reticle drive control system 13 provides a predetermined control signal to the reticle driving device 3 in accordance with each signal from the microprocessor 23, and moves the reticle 1 in the optical axis AX direction by a predetermined amount by the reticle driving device 3. Further, the lens drive control system 16 provides a predetermined control signal to the lens drive device 16 in accordance with each signal from the microprocessor 23, and moves the field lens 6 by a predetermined amount in the optical axis AX direction by the lens drive device 16. . By adjusting the positions of the reticle 1 and the field lens 6, the atmospheric pressure, the temperature, the humidity around the projection lens system 5, and the
The projection magnification error and the symmetric distortion error of the pattern image based on the fluctuation of the temperature and the like are corrected.

Further, the microprocessor 23 controls the projection lens system 5 based on signals from the reticle position detector 15, the lens position detector 17, the atmospheric pressure sensor 19, the temperature sensor 20, the humidity sensor 21, and the lens temperature sensor 22. The focus position of the pattern layer is detected, and the wafer drive control system 14 is controlled based on a signal from the focus detector 18 corresponding to the position of (the surface of) the wafer 9 so that the wafer 9 is positioned at the focus position. . The wafer drive control system 14 provides a predetermined control signal to the wafer drive 11
Moves the wafer 9 in the optical axis AX direction, thereby positioning the wafer 9 at the focus position of the pattern image.

By the above-described operation, the projection magnification of the pattern image is corrected to a predetermined magnification, and the symmetric distortion of the pattern image is suppressed within a predetermined allowable range. And can be accurately overlapped. In addition, since the position of the wafer 9 and the focus position of the pattern image are also matched, a clear pattern image can be projected on the wafer 9.

In this embodiment, the movable field lens 6 for adjusting the projection magnification of the pattern image is constituted by a single lens (G ₁ ), but the field lens 6 may be constituted by a plurality of lenses. . Further, in the present embodiment, in order to detect changes in the projection magnification and symmetric distortion of the pattern image due to changes in atmospheric pressure, air temperature, humidity and lens temperature, a pressure sensor 19, a temperature sensor 20, and a humidity sensor 21 are used. Although the output signal from the lens temperature sensor 22 is used, the pattern image projected by the projection lens system 5 is imaged by the imaging device, and the projection magnification and the symmetry of the pattern image are determined based on the size and shape of the pattern image. A change in distortion may be detected. At this time, if the imaging device is attached to the wafer stage 12, it is possible to detect a change in the projection magnification or the symmetric distortion of the pattern image at a desired time, and the configuration of the exposure device is not complicated.

〔The invention's effect〕

As described above, according to the present invention, in a projection exposure apparatus that projects a pattern of a first object onto a second object by a projection optical system in which both the object side and the image side are telecentric, both the symmetric distortion and the projection magnification can be accurately determined. It is possible to adjust.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of the projection exposure apparatus of the present invention. FIG. 2 is a sectional view showing a specific configuration of a projection lens system of the apparatus shown in FIG. DESCRIPTION OF SYMBOLS 1 ... Reticle 2 ... Reticle chuck 3 ... Reticle drive 4 ... Reticle stage 5 ... Projection lens system 6 ... Field lens 7 ... Lens system 8 ... Lens drive 9 ... Wafer 10 ... Wafer chuck 11 …… Wafer drive device 12 …… Wafer stage 13 …… Reticle drive control system 14 …… Wafer drive control system 15 …… Reticle position detector 16 …… Lens drive control system 17 …… Lens position detector 18 …… Focus position Detector 19 Pressure sensor 20 Temperature sensor 21 Humidity sensor 22 Temperature sensor 23 Microprocessor

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04 H01L 21/30 301,311,321,331

Claims (2)

(57) [Claims] 1. A projection exposure apparatus for projecting a pattern of a first object onto a second object by a projection optical system in which both the object side and the image side are telecentric, wherein a lens of the projection optical system close to the first object is provided. The symmetrical distortion and the projection magnification are changed by moving the projection optical system in the direction of the optical axis, and the first object is moved in the direction of the optical axis of the projection optical system to change the symmetry without changing the projection magnification. A projection exposure apparatus comprising adjusting means for adjusting the symmetric distortion and the projection magnification by changing distortion. 2. A projection exposure apparatus for projecting a pattern of a first object onto a second object by a projection optical system in which both the object side and the image side are telecentric, wherein the first object is projected in an optical axis direction of the projection optical system. A projection exposure apparatus having means for changing symmetric distortion without changing projection magnification by moving the projection exposure apparatus.